CONTROL EFFECTS OF SUTURE ZONES ON DISTRIBUTION OF SOFT ROCK AND ITS ENGINEERING INFLUENCE ALONG SICHUAN-TIBET RAILWAY CORRIDOR

The Sichuan-Tibet railway corridor has high crustal stress, temperature and water pressure. The soft rock is a difficult problem that cannot be ignored. However, the distribution characteristics and engineering effects of the soft rock have not been deeply studied. This paper is based on the geological map of railway corridor, rock mass structure investigation and rebound test as well as microanalysis. It finds that suture zones had obvious control effect on the formation of soft rocks. The paper has the following findings. (1)There are Jinshajiang, Lancangjiang, Nujiang and Yarlung Zangbo suture zones along Sichuan-Tibet railway corridor. Under the influence of the special tectonic activity pattern, temperature and pressure conditions in the suture zone, the soft rocks such as schist, slate, mylonite, cataclasite and damaged rock zones are mainly distributed in the suture zone and on both sides of the boundary faults. (2)The tectonic damage, deformation and metamorphism of rock mass were caused by the plate splitting and converging movement, which led to the deterioration of rock mechanical properties and form soft rocks in the area. (3)The large deformation risk of railway tunnel engineering is higher in the soft rock section controlled by suture zone. Water and mud inrush will be easy to occur when the tunnel engineering passes through tectonic soft rocks near the active bound faults of suture zone. Besides, mountain hazards in suture zones mainly occur in soft rock area with intense river erosion. These findings can provide scientific basis for the prediction and prevention of engineering geological problems of soft rocks along Sichuan-Tibet railway corridor, and also lay foundation for the research of deformation mechanism and engineering prevention technology of soft rock under plate collision and compression.